How to repair broken piano keys

Updated on August 30, 2009

If you are looking for a used piano to buy and don't want to spend much money, chances are, there are probably a great number of used pianos in your city or region, either waiting to be tossed away or sold for a meager price to free some household space. Sellers are usually up to negotiate the price due to major/minor repair requirements, so you will probably find some good pianos for your budget. Apart from the casual tuning after moving the piano to its new home, you might need to do some repairs and adjustments. Although these services might be considered specialized instrument repairs and may cost you money, a piano is a finely manufactured mechanical instrument, and with some basic to no skills, you can make some of these repairs on your own, save money and get acquinted with your new instrument.

On how to open an upright piano to reach the mechanism and the keys, please read this article:

To simply put it, each key on a piano translates the force to a wooden hammer, which in turn hits a string to sound the note. In this tutorial, I will show you how to repair, - in its literal sense-, a broken key. Check the image below:

A -literally- broken piano key :)

A broken key like this is something you don't see very often. Judging from the fact that there were two broken black keys side by side, I would conclude that it might have been a heavy object (like a vase) which has directly fallen onto these keys. The mechanism of a piano much relies on the physical weight of each key and the associated hammer construction, so in order to remedy the friction and ensure a smooth touch, light materials are chosen. Although it is very rare that normal piano playing would cause such damage, the wood might have vains from within, or rapid changes in relative humidity might cause cracks to form. If you have a key, broken and as pictured above, this is an easy but solid fix. Here is a list of what you will need:

Carpenter's glue

Toothpicks and your fingers to apply the glue to the key

2 pressure clamps

No. 100 and No. 400 (one coarse and one fine) sanding paper

scissors

2 very very thin pieces of wood for each key

2 pieces of thicker wooden pieces to help the clamps to press on the applied patch

Materials needed for this recipe ;)

Here is a brief walk through for you to understand what we are going to do:

We will be applying 2 patches on both sides of the broken key, using a strong carpenter's glue. The most important thing is to find or make very thin patches to prevent friction with the neighbouring keys and which will also be thick enough to withstand force when the key will be played later. I recommend making the patch around half a millimeter thick. The repair should be barely visible after the patches are applied. This way the repaired key will not touch the adjescent keys and it will move freely. Another important point is the weight balance of the key. Notice that the break is formed through the hole on the key. This hole is the balancing point. When the key is inserted on its corresponding metal pole, it lays evenly balanced. Since adding a patch will also be adding a minute amount of weight, you should apply the patch to have equal distance from each end to the hole.

Preparing the patches

Find a piece of wooden plank. I happened to have an old furniture, and I simply ripped a small piece from it. It was thicker than it should be, so I used a coarse sandpaper to make it as thin but still solid as possible. After you are done with sanding, the patch should be like a sheet of paper; light weight and flexible.

Use scissors to cut it to a rectangular shape that will fit the side of the key.

Click thumbnail to view full-size

Go and rip a piece of plank off from your old furniture!

Patches, before and after sanding

Applying the glue

If the key has a crack but has not completely separated, try to apply the glue carefully with a toothpick. If the key is almost two pieces, carefully break it into two before applying the glue This will ensure the patch to hold better. Try to use minimum amount of glue, and keep in mind to clean up the excess glue when the pressure is applied.

Gently, apply and clean up excess glue

Press firmly with your fingers for a minute, and align the two pieces of the key before applying the patches to the sides

Applying the patches

Use your fingers to apply a very thin coat of glue on each side of the key, maintaining equal distance from both ends to the hole to insure balanced weight. Apply the patches, and use two pieces of wood to apply pressure homogeneously, then fix with the clamps. Lay the key aside, with the clamps holding patches in place for about 20 minutes to half an hour minimum. After this, remove the clamps. The curing time for the carpenter's glue is usually from 6 to 8 hours. Do not replace the key before it is sufficiently cured; this will insure a strong bond that will withstand force when the key will be struck.

Apply a thin coat of glue and patches

Apply clamps, using 2 pieces of wood to apply equal pressure to the surface

Lay the key aside for half an hour before removing the clamps

After a successful curing, your key is ready to be put back in place. Notice that the patches are thin enough so not to add two much width, well balanced and strong enough to withstand force.

Enjoy!

Click thumbnail to view full-size

Your key is ready to be put back in place after a minimum of 6 to 8 hours of curing

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Comments 6 comments

I performed this repair, the crack was in the same exact area as you indicate there. One thing I found (which required me to redo this) was you had to clamp the keystick down on a flat surface like a glass table, something you know to be flat. I found after performing this repair, the key had a slight bend it it. After clamping the key down to a table (so clamping it down horizondally as well as vertically. I was able to prevent any keydip on the finished product.

Anna 4 years ago

I wounder, how to move this thing it is pretty heavy. LOL. My piano was small and I still had to hire guys to help with moving. That was a scene. www.yourrightmovellc.com

ruth 4 years ago

my piano have several keys that are flat... they won't stay up....how do i fix this? it is upright older piano

Cam 3 years ago

Hi Ruth, I have 2 which also stay flat at the Jack Spring requires replacing on mine to fix them. You may have the same problem.